Browse Prior Art Database

Modifiable Priority Scheme

IP.com Disclosure Number: IPCOM000052754D
Original Publication Date: 1981-Jul-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Chiesa, GL: AUTHOR

Abstract

A large computer system may be thought of as a collection of programs and resources, with the programs making requests of the resources. In the system are several processors and at least one I/O controller. Other resources are main storage and the storage protect array. A program may begin by issuing a storage request which can be either a fetch type or a store type. Each request may use either of two registers in the controller, one for each type of request.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 61% of the total text.

Page 1 of 2

Modifiable Priority Scheme

A large computer system may be thought of as a collection of programs and resources, with the programs making requests of the resources. In the system are several processors and at least one I/O controller. Other resources are main storage and the storage protect array. A program may begin by issuing a storage request which can be either a fetch type or a store type. Each request may use either of two registers in the controller, one for each type of request.

A simplified sequence control matrix is used to select the oldest of all requests. In the related figure, each element in the following table represents a one bit register. The ""V'' bits, if active, indicate that this request is waiting for service. The ""A'' bits indicate which one of every pair of possible requests has been waiting longer; for example, if the ""6A2'' bit is on, this means that request 2 (a P2 fetch) has been waiting for service longer than request 6 (a P3 store), whereby request 6 is after request 2. All other things being equal, request 2 would be serviced before request 6. Note that there is no 2A6 bit, as this is the inverse of the 6A2 bit. Priority Tables ##

In this priority scheme, priority is always given to the oldest request in the queue. In some systems it may be favorable to allocate highest priority to one or more requests, without regard to the age of any of the requests. This may be because some of the requests are executing a job where performance...